In many industrial processes, items have to be transported from one place to another, or through a processing area, where the items are treated in different ways. A common example is an assembly line, where items are passing from one station to the other and where e.g. new parts are mounted at each station. Other examples are treatment of items, such as painting, annealing or irradiation, where the items pass through a processing area in which the treatment is performed. In all such cases, different kinds of conveyor systems are necessary.
A common type of conveyor system comprises a conveying means, e.g. a linked chain or a wire, which is formed as a closed loop. The conveying means is typically driven by a motor using a wheel or gear wheel. Supporting members are attached pivotably at the conveying means, typically at regular distances. The supporting members are connectable to carriers, in which the items are transported, or to the items themselves. The position of the supporting member is typically defined by the gravitational forces, in which cases the carriers typically always are directed downwards or by guiding means. When transporting items along a path including alternating horizontal and vertical sections, the dimensions of the transported items will play an important role. When making a 90-degree turn, from horizontal to vertical, one item may collide with the following, if not enough space is provided between them. One may from simple model reasoning understand that the space between the items has to be at least equal to the item height, in order to avoid collision. Conveyor arrangements of this type thus typically transport items separated with a certain distance.
In many applications, the interspace between the items is disadvantageous. If the items are going through a treatment, the efficiency of the treatment is reduced by the space between the items. Also, e.g. at loading or unloading, it is normally advantageous if there is no space between the items.
In the patent application GB 2 067 968, a conveyor arrangement is disclosed, which shows a planar closed-loop conveyor. A positioning arrangement is pivotably attached to a linked chain, and a carrier means is rotatably attached to the positioning arrangement. A follower member provided with a rotatable roller is attached at an arm at the positioning arrangement. The pivotable attachment point follows the chain path, while the follower member follows a guide means. The relative distance between the guide and the chain path decides the angle of the positioning arrangement and thus the relative position of the carrier means. A second positioning arrangement is rigidly attached to the carrier means. Two follower members are arranged at this second positioning arrangement, following two further guides. The relative distance between the two further guides determines the angle of the second positioning arrangement. By suitable choice of guiding structures, the carrier means can be positioned in almost any arbitrary direction. This positioning may indeed be very flexible, but the use of a multitude of guides and follower members are far too complex in most cases and occupies too much space for many treatment applications.
In the patent application DE 195 10 649, a conveyor device is disclosed, which provides for an adaptive distance between the transported items. A conveying linked chain supports carrier means along a path. At a chain joint between the attachment points of the carrier means, an arm member is attached. The arm member is provided with a follower member, which is guided along a rail arrangement, forcing the chain to bend. The bent chain makes the carrier means to be positioned closer to each other, i.e. gives rise to the adjustable distances. This conveyor has the disadvantage that the conveying means, i.e. the chain, is bent at the same time as it is supposed to drive the carrier means forwards. The forces and friction involved in such arrangements are generally high, and the total arrangement is space requiring.
In many applications, the available space around the conveyor path is limited. A general disadvantage with conveyor arrangements for adjustable item distances is that they demand quite complex and space requiring guiding means. Furthermore, angle-determining arm structures according to prior art have limited angle strokes, within which they are stable and well determined.